diff --git a/src/core/schema_adapters.py b/src/core/schema_adapters.py
index 8707a6d32..5e3f5f6a9 100644
--- a/src/core/schema_adapters.py
+++ b/src/core/schema_adapters.py
@@ -445,6 +445,22 @@ class ListAuthorizedPropertiesResponse(AdCPBaseModel):
     last_updated: str | None = Field(None, description="ISO 8601 timestamp of when authorization list was last updated")
     errors: list[Any] | None = Field(None, description="Task-specific errors and warnings")
 
+    def dict(self, **kwargs):
+        """Override dict to use model_dump with exclude_none=True for AdCP compliance.
+
+        FastMCP may use dict() for serialization instead of model_dump().
+        This ensures optional fields with None values are excluded from the response.
+        """
+        return self.model_dump(**kwargs)
+
+    def __iter__(self):
+        """Override iteration to exclude None values for AdCP compliance.
+
+        When dict() or json.dumps() iterates over the model, it will only include
+        non-None fields. This ensures the response is spec-compliant.
+        """
+        return iter(self.model_dump().items())
+
     def __str__(self) -> str:
         """Return human-readable message for protocol layer.
 
diff --git a/src/core/tools/properties.py b/src/core/tools/properties.py
index b41f728a2..b8334e5b5 100644
--- a/src/core/tools/properties.py
+++ b/src/core/tools/properties.py
@@ -198,11 +198,14 @@ def _list_authorized_properties_impl(
             # Create response with AdCP spec-compliant fields
             # Note: Optional fields (advertising_policies, errors, etc.) should be omitted if not set,
             # not set to None or empty values. AdCPBaseModel.model_dump() uses exclude_none=True by default.
-            response = ListAuthorizedPropertiesResponse(
-                publisher_domains=publisher_domains,  # Required per AdCP v2.4 spec
-                advertising_policies=advertising_policies_text,
-                # errors omitted - only include if there are actual errors
-            )
+            # Build response dict with only non-None values
+            response_data = {"publisher_domains": publisher_domains}  # Required per AdCP v2.4 spec
+
+            # Only add optional fields if they have actual values
+            if advertising_policies_text:
+                response_data["advertising_policies"] = advertising_policies_text
+
+            response = ListAuthorizedPropertiesResponse(**response_data)
 
             # Log audit
             audit_logger = get_audit_logger("AdCP", tenant_id)